Embodiments of the present invention relate to a solid-state lithium battery having an electrolyte and related fabrication methods.
Lithium batteries are used in applications that require a battery with a high energy density such as, for example, portable electronics, medical devices and space systems. Solid-state, lithium, thin film batteries provide long battery cycle life, low battery capacity fade properties, good operational temperature range, safety and other advantages over conventional battery systems. A typical solid-state lithium battery comprises one or more battery cells, each cell having a set of battery component layers on or between supports. The battery component layers cooperate to store electrical charge and generate a voltage. The battery component layers typically include an electrolyte between electrodes, such as an anode, cathode, anode current collector and cathode current collector. Lithium thin film batteries include those batteries in which the battery component layers are thin solid films which typically have thicknesses of less than about 1000 microns. Such lithium batteries can include one or more battery cells which are stacked together and connected in series or in parallel to provide more power or energy.
However, the electrolyte of the solid-state lithium batteries often has process fabrication issues and operational problems. For example, electrolyte layers of lithium-containing material, such as lithium-phosphorous-oxygen-nitrogen (LiPON), would sometimes delaminate from the underlying layers of the battery cell for unknown reasons. The cause of delamination of the deposited electrolyte layers was difficult to identify as this can result from a number of factors, including the thickness of the electrolyte, the difference in thermal expansion between the electrolyte and underling battery layers, and even the deposition microstructure of the electrolyte. Delamination of the electrolyte reduces production yields and loss of battery capacity over time can result in degraded performance and unexpected failure during battery operation. Battery cells with a LiPON electrolyte layer were also discovered to have low battery energy capacities after as little as 30 charge/discharge cycles.
For these and other reasons, further developments and improvements in the structures, and methods of fabrication of, an electrolyte for a solid-state lithium battery, are continuously being sought.